Specifications for Long Term Evolution (LTE) are drafted by a Wideband-Code Division Multiple Access (W-CDMA) standardization group 3rd Generation Partnership Project (3GPP). The LTE is a standard specification developed from an extended technique High Speed Packet Access (HSPA) of the W-CDMA. In the LTE, high speed communications of higher than 100 Mbps in downlink and higher than 50 Mbps in uplink are realized to achieve delay reduction and frequency utilization.
Subsequent introduction of the LTE may lead to a mixture of existing mobile communication systems and the LTE. Such an existing system may include a W-CDMA based mobile communication system.
In a mobile communication system, a mobile apparatus measures reception level or reception quality of a predefined frequency. The predefined frequency includes a frequency for a serving cell or a frequency different from that for the serving cell. The serving cell may be a cell for the LTE. Also, the predefined frequency may include a frequency for a Radio Access Technology (RAT) different from the LTE. The RAT may include a W-CDMA based mobile communication system. The frequency band for a Radio Access Technology (RAT) different from the LTE may consist of the same frequency band as the LTE or a different frequency band.
If measurements for a frequency band different from the frequency band for the serving cell are performed at a mobile apparatus, a period for measuring the frequency band is configured between a base station apparatus and the mobile apparatus. This period is also referred to as a measurement gap. If there is a likelihood that the mobile apparatus may be caused to conduct handover to the frequency band different from the frequency band for the serving cell, the base station apparatus indicates the mobile apparatus to activate the measurement gap and measure a predefined frequency band. Here, a case where there is a likelihood of causing the mobile apparatus to conduct handover may correspond to the case where communication quality is poor in a present communication area and another base station apparatus is present around the base station apparatus. The base station apparatus determines timings of causing the mobile apparatus to activate or deactivate the measurement gap. In order to determine the timings, the base station apparatus indicates the mobile apparatus to measure communication quality for areas during communications. In the measurement gap, the mobile apparatus measures a frequency band different from a frequency band for a serving cell, and the base station apparatus (eNodeB) does not transmit data to the mobile apparatus. This is because the mobile apparatus cannot transmit and receive any data in the measurement gap.
If the mobile apparatus detects degradation of the communication quality during the activated measurement gap, the mobile apparatus deactivates the measurement gap and requests reconnection to the base station apparatus. The degradation of communication quality may be referred to as “squelch”.
When the base station apparatus indicates reconfiguration, such as measured contents, to the mobile apparatus, the base station apparatus may transmit difference information between that reconfiguration and the previously indicated configuration. The transmission of difference information is defined as delta configuration. For example, when the base station apparatus indicates reconfiguration, such as measured contents, to the reconnected mobile apparatus, the base station apparatus may transmit the difference information between configuration indicated before the reconnection and the reconfiguration. Between the pre-reconnection and the post-reconnection, the mobile apparatus inherits the configuration indicated before the reconnection. In other words, even if the reconnection occurs, the configuration held in the mobile apparatus remains unchanged.
See TS36.331 V9.1.0 2009 12 for further details, for example.